Epoxy composites produced via sodium alginate‐mediated <scp>Ca</scp> crosslinking of <scp>MXene</scp> and boron nitride fillers with excellent thermal conductivity and electromagnetic interference shielding effectiveness

Abstract This study investigates novel polymer composites for enhanced thermal conductivity and electromagnetic interference (EMI) shielding. By incorporating sodium alginate‐mediated Ca crosslinked MXene and boron nitride fillers into an epoxy matrix, the composites exhibit significantly improved thermal, electrical, and mechanical properties. Surface treatment enhanced filler dispersion and interfacial bonding by introducing hydroxyl groups, which improve compatibility between the fillers and the matrix, thereby reducing agglomeration and creating robust thermal and electrical conduction networks. Hot‐pressing method further increases composite density by eliminating internal voids and aligning the fillers more effectively, resulting in superior characteristics. The best performing hot‐pressed composite achieved a through‐plane thermal conductivity of 7.45 W/m K, excellent EMI shielding effectiveness of 58.3 dB, along with a tensile strength of 37.2 MPa and an elongation as high as 3.8%. These enhancements make the composites highly suitable for advanced electronic devices where efficient heat dissipation and EMI shielding are critical. Highlights Surface treatment improves filler dispersion and compatibility. High‐filler composites are fabricated by hot‐pressing method. MX‐CA‐BN/EPH composites achieve 7.45 W/m K thermal conductivity. Enhanced EMI shielding effectiveness of 58.3 dB.